Pressure vessel for forming apparatus



April 23, 1968 F. J. FUCHS, JR

PRESSURE VESSEL FOR FORMING APPARATUS 5 Sheets-Sheet 1 Filed March 1,1965 INVENTOR fhrzalaz'lkc/s; Jr; l /4W ATTORNEY April 23, 1968 F, J,FUC JR 3,379,043

A ril 23, 1968 Filed March 1, 1965 P. J. FUCHS, JR

PRESSURE VESSEL FOR FORMING APPARATUS 5 Sheets-Sheet 5 April 23, 1968 F.J. FUCHS, JR

PRESSURE VESSEL FOR FORMING APPARATUS 5 Sheets-Sheet 4 Filed March 1,1965 April 23, 1968 F. J. FUCHS, JR 3,379,043

PRESSURE VESSEL FOR FORMING APPARATUS Filed March 1; 1965 5 Sheets-Sheet5 &

United States Patent 3,379,043 PRESSURE VESSEL FOR FORMING APPARATUSFrancis J. Fuchs, Princeton Junction, N.J., assignor to Western ElectricCompany, Incorporated, New York, N.Y., a corporation of New York FiledMar. 1, 1965, Ser. No. 436,128 Claims. (CI. 7256) ABSTRACT OF THEDISCLOSURE A pressure vessel including a forming cylinder for containingfluid which is pressurized by a piston movable into the cylinder. Theforming cylinder is expandable in response to a predetermined fluidpressure to allow a portion of the pressurized fluid to flow out of thecylinder, past the piston, into another cylinder, or succession ofcylinders, spaced from and surrounding the forming cylinder. Thepressurized fluid in the surrounding cylinder, or cylinders, exertsinward forces on forming cylinder counteracting the radial forcesgenerated by the piston acting on the fluid contained in the formingcylinder.

This invention relates to an ultra-high pressure metal forming apparatusand more particularly to a forming apparatus having facilitiesresponsive to the generation of ultra-high pressures within a formingcylinder for applying opposing or restraining forces to the outside ofthe cylinder.

The ductility of metals such as steel, brass, aluminum, molybdenum, andcopper increases tremendously when a high hydrostatic pressure isapplied to the metal. Due to this increased ductility, operations suchas deep drawing or metal forming are considerably facilitated ifaccomplished with high fluid pressures acting on the metal within aforming cylinder. Present forming presses are not readily adapted towithstand the internal pressures required to utilize this principle ofincreased metal ductility at high pressure.

Difliculties involving the design of a piston-cylinder apparatus towithstand high pressures are considerable. The primary limitation onhigh pressure apparatus is the strength of the materials used inconstruction. At prescut, the maximum fatigue strength available insteel is 130,000 psi. for unlimited cycles, to a maximum practical valueof 150,000 psi. for about 100,000 cycles. Even by using a series ofshrink-fitted cylinders, the useful strength levels can be boosted onlyto 300,000 p.s.i. a value still short of desired high pressures inexcess of 500,000 p.s.i. which can be utilized to take advantage of theincreased ductility of metals encountered at high forming pressures.

Attempts have been made in the past to attain high pressures by using amulti-stage apparatus whereby a forming cylinder is surrounded by afirst pressure vessel which is surrounded by a second pressure vessel,etc. In this type of apparatus, pressurized fluids are introduced intothe forming cylinder and the pressure vessels by separate externalpressure sources. If any of the external pressure sources should failfor any reason, such as a faulty valve, failure of the forming cylinderor pressure vessel immediately results.

Some multi-stage apparatus directly pass pressurized fluid from theforming cylinder into surrounding vessels. However, it is very difiicultto generate high pressures using this apparatus.

Furthermore, when multi-staging is used, opposing radial forces actingon the forming cylinder wall result in a pinch-off effect in which themetal of the cylinder wall tends to flow longitudinally away from thearea being subjected to the opposing radial forces. In practice,

multi-staging is extremely difiicult to utilize and difficulty increaseswhen more than two stages are used.

It is an object of this invention to provide a new and improvedultra-high pressure metal-forming press.

Another object of the invention resides in a press for generating andwithstanding ultra-high pressures of over 500,000 p.s.i.

A further object of the invention is to provide a forming cylinderhaving facilities responsive to internally generated pressures forapplying balancing forces to the outer surface to compensate forultra-high pressures generated within the cylinder.

Another object of the invention resides in the utilization of theelastic deformation of a forming cylinder to vent high-pressure fluidout to an annular chamber surrounding the cylinder to providecounter-acting forces against the outer surface of the cylinder.

Another object of this invention is to provide a forming press havingfacilities to counteract the longitudinal forces generated in theforming cylinder by the opposing radial forces acting on the formingcylinder.

An additional object of the invention resides in the use of a series ofcylinders having facilities to pass fluid from the inner cylinder to theouter cylinders successively, each cylinder being spaced apart from theother and having facilities for confining fluid under pressure in eachof these spaces so that the pressure within the inner cylinders will becounteracted by the decreasing pressures within the successive outercylinders.

Another object of this invention is the provision of a forming presswherein longitudinal or pinch-off forces generated within a formingcylinder Wall are counteracted by opposing forces generated in responseto the forces generated within the cylinder.

A further object of this invention is to provide a forming pressutilizing a series of concentric cylinders with pressure equalizationfacilities responsive to a decrease in pressure within an innercylinder.

With these and other objects in view, the present invention contemplatesa deep drawing ultra-high pressure metal forming press having facilitiesresponsive to the forces generated within the press for generatingcompens'ating forces to overcome the deleterious eifedts of the internalforce's on the components of the press. More particularly, a metal blankis placed within a high-pressure forming cylinder. Fluid is introducedinto the cylinder, and a piston is moved to act on the fluid to generatehigh pressures against the metal blank. The forming cylinder w allelastically expands when a predetermined pressure is reached allowingpressurized fluid to flow past the piston into another cylinder orsuccession of cylinders spaced from and surrounding the formingcylinder. The pressurized fluid acting within the surrounding cylinderexerts inward forces on the forming cylinder, counteracting the radialforces generated by the piston acting on the fluid. These counteractingforces decrease the differential pressure across the forming cylinderwall, thereby decreasing the stresses therein. Furthermore, facilitiesare provided to exert longitudinal forces on the forming cylinder tocounteract those longitudinal forces generated by the opposing radialforces. By using such apparatus as described, it is possible to exertultra-high pressures in the nature of 500,000 p.s.i. or greater on ametal blank, and to consequently draw the metal blank through a formingdie.

Other objects and advantages of the present invention will be apparentfrom the following detailed description when considered in conjunctionwith the accompanying drawings, wherein:

FIG. 1 is a front view partially in section of a highpressure formingapparatus embodying the principles of the present invention;

FIG. 2 is a sectional view taken along line 2--2 of FIG. 1 showing themetal blank positioned in a forming cylinder secured by a threaded ring,and a segmented cylinder surrounding the forming cylinder;

FIG. 3 is an exploded front sectional view showing the elementscomprising a limited diameter seal on a highpre'ssure piston;

FIG. 4 is a cross-sectional front view of an alternative embodiment of ahigh-pressure forming apparatus;

FIG. 5 is a front view partially in section of another alternativeembodiment of a high-pressure forming appara'tus;

FIG. 6 is a partial enlarged view of an end restraining member andintermediate cylinder taken from FIG. 5 and panticul'arly showing theforces acting on the member and cylinder;

FIG. 7 is a cross-sectional front view of a further embodiment of a highpressure forming apparatus;

FIG. 8 is a partial view taken from FIG. 7 showing the forces acting ona wear-resistant sleeve;

FIG. 9 is a partial view taken from FIG. 7 showing a wear-resistantsleeve forced off a piston into a forming cylinder;

'FIG. 10 is a front view partially in section of another alternativeembodiment of a high-pressure forming apparatus; and

FIG. 11 is a detailed front sectional view of a drawing and extrusiondie shown in FIG. 5.

Referring now to FIG. 1, there is shown one embodiment of an ultra-highpressure metal forming apparatus for forming a circular metal blank 100into a tubular cup-shaped member 10 1 (as shown by the dotted lines).The ultra-high pressure metal forming apparatus includes a formingcylinder 102 having a bore 103 therethrough and a partially threadedcounterbore 104, both of which 3 are filled with fluid 105 during theoperation of the apparatus.

The forming cylinder 102 has an upper beveled surface 116, a lowerbeveled surface 117, and an intermediate shoulder 106 formed by thejuncture of the bore 103 and the counterbore 104. A forming die 107,having an orifice therethrough, is tightly fitted into the counterbore104 in abutting relationship with the shoulder 106.

The metal blank 100, having a diameter of a few thousandths of an inchsmaller than the diameter of the countenbore 104, is positioned on topof the forming die 107 and is fixedly held by a hollow externallythreaded ring 108, the threads of which are interrupted by severalaxially extending grooves 109 (see FIG. 2) to provide passageways forthe fluid 105 contained in counterbore 104.

The purpose of the grooves 109 is to introduce highpress'ure fluid fromcounterbore 104 into the annular space 110 defined between the peripheryof the metal blank .100 and the inner wall of the forming cylinder 102.The high-pressure fluid acts against the peripheral edge of the metalblank 100 to compressively force the material of the blank 100 towardand into the orifice of the forming die 107. This compressive forcereduces the tensile force necessary to draw the blank 100 through theforming die 10-7.

A first piston 113 is mounted for movement within the counterbore 104 ofthe forming cylinder 102. A limited diameter seal generally designatedas 1'14 is attached to the lower end of the first piston 113. The seal114 (see FIG. 3) includes a first, expandable bevelededged annulus 120which is urged outwardly toward the inside wall of the forming cylinder102 by an inner beveled-edged disc or spreader 122. An outer disc orlimiter 123 is secured against the inner disc 122 by a retaining screw1'25, and has an axially extending flange 130 on the periphery thereofwhich limits the di'a'metrical expansion of annulus 120.

A high-pressure ram 118, forming part of a conunerical- 1y availablehigh-pressure press, engages and moves the first piston 113 to generatehigh fluid pressures within the counterbore 104 and against the uppersurface and the periphery of the metal blank 100. A second piston 1 19,mounted for movement Within bore 103 of forming cylinder 102, isindependently movable by a ram 121, forming part of a commerciallyavailable high-pressure press, to generate a back-up pressure againstthe lower surface of the metal blank 100. The back-up pressure issufliciently high so as to increase the ductility of the metal blank100, but is substantially lower than the pressure in counterbore 104 sothat there is a large pressure differential for drawing the metal blankinto and through .the forming die 107. For example, the back-up pressurefor a molybdenum blank may be approximately 350,000 p.s.i., while thedrawing pressure may be 500,000 psi.

The forming cylinder 102 is surrounded by a hollow cylinder 126 made upof a plurality of separate segments 126a, 126b, etc. (see FIG. 2). Thesegmented cylinder .126 has an inner beveled surface 132 injuxtaposition with the lower beveled surface 117 of the forming cylinder102. The top portion of the se mented cylinder 126 is internallythreaded at 134 to receive a sleeve-like end restraining member havingexternal threads 133 thereon. End restraining member 115 has a bore 135therethrough in alignment with the counterbore 104 for receiving thefirst piston .113. Sleeve-like end restraining member 115 has a beveledsurface 131 in juxtaposition with the upper beveled surface 116 of theforming cylinder 102. The segmented cylinder 126 is tightly confinedwithin a hollow intermediate cylinder 127, which in turn is enclosedwithin a casing 129 which is spaced from the intermediate cylinder 127to provide an annular space 128 (slightly exaggerated) for receivingfluid therebetween.

The casing v129 has a passageway 147 therethrough for passing fluid fromthe annular space 128 to an overbalance valve 148. The over-balancevalve has two chambers 149 and 150 therein for receiving fluid,respectively, from the annular space 128 and the high-pressure ramcylinder which is not shown. A bore 151 connects the two chambers, 149and 150. A stepped piston 152 is slid'ably mounted within the bore 151and the chamber 150. The piston 152 moves into chamber 150 uponsubjection to a predetermined pressure ratio, permitting the fluid inthe chamber 149 and the annular space 128 to pass through a passageway153 into a reservoir not shown. The valve 148 is utilized to prevent thefluid contained within the annular space 128 from urging the segmentedcylinders 126 inwardly upon retraction of the piston 113 from theforming cylinder 102 after the forming operation is completed. Toillustrate, when the piston 113 is withdrawn, the pressure in thecounterbore 104 drops and the pressure in the high-pressure ram cylinderdrops proportionately. Since the pressure of the fluid in the annularspace 128 remains the same, the ratio between the pressure in theannular space 123 and the pressure in the high-pressure ram cylinderincreases. When this ratio increases above a predetermined value, theover-balance valve 148 opens to vent fluid from the annular space 128through the passageway 153. The valve 148 closes when sutficient fluidis vented so that the predetermined ratio is again attained.

The casing 129 is internally threaded at a lower portion .133 and anupper portion 139. A first threaded ring having a groove 141 therein toreceive an annular seal 142 cooperates with the lower threaded portion138 of the casing '129 to enclose the bottom of the annular space 128. Asecond threaded ring 144 having a groove 145 therein to receive anannular seal 146 cooperates with the upper threaded portion 139 of thecasing 129 to completely enclose the annular space 128.

To prevent overstressing the ultra-high pressure apparatus, the secondthreaded ring 144 and the seal 146 are adjustable to permit fluid 105contained within the enclosed annular space 128 to vent past the sealand threads to the atmosphere if a predetermined pressure is reachedtherein. It is not contemplated that fluid would vent to the atmosphereduring a normal operation, rather it would vent only in the event ofmalfunction of any of the high pressure equipment.

When the pressure in counterbore 104 is increased to a sufficiently highvalue, the cylinder 102 elastically expands allowing fluid 105 to escapepast the high-pressure seal 114, through the space between the outersurface of the first piston 113 and the inner surfaces of the formingcylinder 102 and the sleeve-like end restraining memher 115 and theninto a radial aperture 124. This radial aperture 12 extends through thesleeve-like member 115, a segment of the cylinder 126 and theintermediate cylinder 127 to pass fluid into the annular space 128.High-pressure fluid introduced into the annular space 123 acts on theintermediate cylinder 127, which in turn forces the segmented cylinder126 inwardly against the forming cylinder 102.

The inward force exerted by the segmented cylinder 126 on the formingcylinder 102 opposes the outward force generated within the counterborev104 and the bore 102 of the forming cylinder 102. When the inward forceof the segmented cylinder 126 increases to a suflicient extent, theforming cylinder 102 contracts and moves against the seal 114 therebyresisting the flow of fluid 105.

Since the outer peripheral area of the intermediate cylinder 127 issubstantially greater than the outer peripheral area of the formingcylinder 102, the inward pressure of cylinder 126 against the formingcylinder 102- is substantially greater than the pressure of the fluidwithin the annular space 128. More particularly, the pressure P1 of thefluid contained within the enclosed annular space 128 multiplied by theperipheral area A1 of the intermediate cylinder 127 equals a force F1acting on the cylinder 127. The force F1 is transmitted through theintermediate cylinder 127 and the segmented cylinder 126 to act againstthe forming cylinder 102. However, since the peripheral area A2 of theforming cylinder 102 is substantially smaller than the peripheral areaA1 of the intermediate cylinder 127, the pressure P2 on the formingcylinder .102 is greater than the pressure P1 on the intermediatecylinder '127. In other words, F1=P1 A1 and F2=P2 A2. But F1=F2 sincethe force is transmitted through the cylinders 120 and 127 so that PlA2=Pl A1. Since A1 is greater than A2, P2 is greater than P1. Thus,P2=A1/A2 P1.

The pressuirzed fluid contained within the counterbore 104 and thepressurized fluid contained within the annular space 128 generateopposing forces F7 and F2, respectively, on the forming cylinder 102resulting in a condition known as pinch-off, whereby opposinglongitudinal forces F3 are generated in the forming cylinder 102 asshown in FIG. 1. Pinch-off occurs when opposing internal and externalforces acting on a cylinder wall are so high that the metal of thecylinder flows longitudinally away from the area subjected to theopposing forces, thereby decreasing the thickness of the cylinder walluntil rupture occurs.

To counteract the longitudinal pinch-off forces, the forming cylinder102 is firmly supported at both ends. The end restraining member 115 isthreaded into the segmented cylinder 126 so that the beveled surface 131thereof abuts against the beveled surface 116 to support the upper endof the forming cylinder 102. As shown by the force diagram in FIG. 1,end restraining member 115 exerts a normal force F4 perpendicular to thebeveled surface 116 of the forming cylinder 102. The normal force F4 hascomponent forces F5 and F6 which respectively oppose the longitudinalpinch-off force F3 and the outward force F7 generated by thehigh-pressure fluid 105 contained within the counterbore 104.

The lower end of the forming cylinder 102 is supported at the beveledsurface 117 by the abutting beveled surface 132 of the segmentedcylinder 126. As shown by the force diagram in FIG. 1, the segmentedcylinder 126 exerts a normal force F4 perpendicular to the beveledsurface 117 of the forming cylinder 102. The normal force F4 hascomponent forces F5 and F6 which respectively oppose the longitudinalpinch-off force F3 and the outward force F7 generated by thehigh-pressure fluid 105 contained within the bore 103.

The end restraining member 115 is under a high compressive load duringthe forming operation, which tends to shorten it thus decreasing thepitch of the external threads 133 thereon. Meanwhile, the matchingthreads 1334 on the segmented cylinder 126 are under tension andexperience an increase in the pitch of the threads 134. This results inthe end threads being loaded more than the intermediate threads. Toeliminate this problem and to provide uniform loading of the threadsfrom end to end, the pitch of the threads 133 on the end restrainingmember 115 is increased by an amount equivalent to the change in lengthof the end restraining member 115 under the compressive load. Thus, whenthe end restraining member 115 is under a compressive load during theforming operation, the pitch of the threads 133 will equal the pitch ofthe threads 134 on the segmented cylinder 126 thereby providing uniformthread loading.

OPERATION In use of the apparatus, the first piston 113 is initiallycompletely withdrawn. The second piston 119 is partially inserted intothe bore 103 of the forming cylinder 102 and hydraulic fluid 105 isintroduced or poured into the bore 103. The forming die 107 is thenplaced against the shoulder 106 of the forming cylinder 102, after whichthe metal blank is placed on the upper surface of the forming die 107,and the ring 108 is threaded into the forming cylinder 102 to fixedlyposition and hold the metal blank 100 against the forming die 107.Hydraulic fluid is then introduced or poured into the counterbore 104and the first piston 113 is moved into the counterbore 104.

Next, the independently driven high-pressure ram 118 and back-up ram 121are actuated to respectively move the first piston 113 and the secondpiston 119 toward the metal blank 100. As the piston 113 moves, thepressure in counterbore 104 increases until the forming cylinder 102 isstrained and elastically expands permitting fluid 105 to escape past thelimited diameter seal 114, through the radial aperture 1 4 and into theenclosed annular space 128 between the intermediate cylinder 127 and thecasing 129. The pressurized fluid contained within the annular space 123acts on the intermediate cylinder 127 which in turn forces the segmentedcylinder 126 inwardly to support the forming cylinder 102. The inwardpressure exerted by the segmented cylinder 126 on the forming cylinder102 reduces the net pressure across the wall of the forming cylinder 102so that the forming cylinder 102 contracts sufficiently to again engagethe seal 114, thereby restricting the flow of pressurized fluid 105. Asthe pressure continues to increase within the counterbore 104, the wallof the cylinder 102 alternately expands from the increasing internalpressure, and contracts from the external pressure of the segmentedcylinder 126.

The beveled surfaces 131 and 132 of the end restraining member and thesegmented cylinder 126, respectively, support the ends of the formingcylinder 102 to prevent pinch-off or reduction of wall thickness clue tothe high opposing radial forces acting on the forming cylinder 102.

The pressure in bore 103, generated by the movement of the second piston119, is sufficient to increase the ductility throughout the metal blank100; but is substantially lower than the pressure in counterbore 104,generated by the first piston 113. The ultra-high pressure fluid incounterbore 10 acts perpendicular to the metal blank 100 tending to drawit through the orifice of the forming die 167. Simultaneously, theultra-high pressure fluid 105 passes through the grooves 109 in thethreaded ring 108 into the annular space 110 to force the periphery ofthe metal blank 100 inwardly tending to extrude the blank through theorifice of the forming die 107. This extruding force reduces the tensileforces necessary to draw the metal blank 1% through the forming die 167.The combination of the drawing pressure and the extruding pressureforces the blank Hi0 through the die 197, aided by the increasedduetility resulting from the bacleup pressure, to form a cup shapedmember 121 of substantially equal thickness throughout.

After the metal blank 180 is drawn and formed, the first piston 113 iswithdrawn, the threaded ring 1G8 is removed, and the newly-formedtubular cup-shaped member 101 is extracted from the forming cylinder1G2.

ALTERNATIVE EMBODIh lEFT Referring now to FIG. 4, there is shown analternative embodiment of a high-pressure metal forming apparatus forforming a metal blank 1% into a tubular cup-shaped member 101. Thealternative embodiment is similar in many respects to the firstembodiment which is described in great detail. Accordingly, repetitiousdescriptions of similar or identical elements are not included in thefollowing description, and reference for further details should be madeto the description of the first embodiment. The alternative embodimentincludes a forming cylinder 2422 having a bore 203 therethrough and acounterbore 264, both of which are filled with fluid during the formingoperation. The forming cylinder 262 has an upper beveled surface 266 anda lower beveled surface 207'. A forming die 107, as shown in PEG. 1, istightly fitted into the counterbore 2&4 and a metal blank 1% is fixedlyheld thereagainst by a hollow threaded ring 168, the threads of whichare interrupted by several axially extending grooves, identical togrooves 139 as shown in FIG. 2.

A hollow segmented cylinder 211, having an upper comically-shapedcounterbore 222 and a lower conicallyshaped counterbore 213, surroundsthe forming cylinder 202. The counterborcs 212 and 213 have internalthreads which cooperate respectively with the external threads of anupper eonically-shaped hollow end restraining member 215 and a lowercomically-shaped hollow end restraining member 216. The upper endrestraining member 215 has a beveled surface 217 which abuts against theupper beveled surface 206 of the forming cylinder 202 to provide supportthereto. The lower end restraining member 216 has a beveled surface 218which abuts against the lower beveled surface 207 of the formingcylinder 292 to provide support thereto.

A hollow intermediate cylinder 221 tightly surrounds the segmentedcylinder 211. A casing 222 surrounds and is spaced from the intermediatecylinder 221 to provide an annular space 223 therebetween. Casing 222has an internally threaded bottom portion for receiving a threaded ring224. Ring 224 has a groove 226 therein to receive an annular seal 227which effectively seals the bottom of annular space 223. Casing 222 hasan internally threaded top portion for receiving a second threaded ring228. Ring 228 urges an annular seal 231 against the intermediatecylinder 221 and the casing 222 to effectively seal the top of annularspace 223 to prevent hi h-pressure fluid from escaping therefrom. Aradial aperture 225 through upper end restraining member 215, segmentedcylinder 211., and intermediate cylinder 221, communicates the inside ofthe end restraining member 215 with the enclosed annular space 223. Anover-balance valve, not shown, similar to the valve 143 shown in FIG. 1,is connected to communicate with the annular space 223.

A first stepped piston 234 has an upper portion 235 of one diameter anda lower portion 236 of a smaller diameter. The upper portion 235 isslidably mounted for movement within the upper end restraining member215 and the lower portion 236 is slidably mounted for movement withincounterbore 264 of forming cylinder 202. An annular pressure chamber 237is defined between the lower portion 236 and the inner surface of theend restraining member 215. The piston 234 has a seal generallydesignated as 238 attached to the lower end thereof. This seal issubstantially similar to the seal shown in FIG. 3 and described in thefirst embodiment. A seal 239 is positioned at the juncture of the upperportion 235 and the lower portion 236 to retain high-pressure fluidwithin the annular pressure chamber 237.

A second stepped piston 241 has a lower portion 242 of one diameter andan upper portion 243 of a smaller diameter. The lower portion 242 isslidably mounted for movement within the lower end restraining member216 while the upper portion 243 is slidably mounted for movement withinthe bore 263 of forming cylinder 202. An annular pressure chamber 247 isdefined between the upper portion 243 and the inner surface of the lowerend restraining member 216. A seal 244, substantially similar to seal238, is attached to the end of the second stepped piston 241. Anotherseal 246 is positioned at the juncture of lower portion 242 and upperportion 243 of the second stepped piston 241 to retain pressurized fluidwithin the annular pressure chamber 247. The stepped pistons 234 and 241are independently movable by commercially available high-pressurepresses 248 and 249.

OPERATION In the operation of the high-pressure apparatus, the r rststepped piston 234 is completely withdrawn and the second stepped piston241 is partially withdrawn. Hydraulic fluid is then introduced or pouredinto the lower end restraining member 216, the forming cylinder 202, andthe upper end restraining member 215. Next, the forming die 107, metalblank 10%), and ring 1% are inserted into the fluid-filled counterbore204. The first stepped piston 234 and second stepped piston 241 are thenindependently moved inwardly toward the metal blank 1%. As the pressurebuilds up in the counterbore 204, the forming cylinder 202 isincreasingly strained until it elastically expands allowing pressurizedfluid to pass between the seal 238 and the inner surface of the formingcylinder 2G2 into the annular pressure chamber 237. Similarly,high-pressure fluid expands the lower portion of the forming cylinder232 to provide a passageway for fluid into the second annular pressurechamber 247.

The pressurized fluid in the first and second pressure chambers 237 and247 provides radial support for the smaller diameter portions 236 and243 of the first stepped piston 234 and the second stepped piston 241.This radial support prevents mushrooming of the pistons from the highpressures acting on the ends thereof. Mushrooming occurs when a pistonis subjected to a high compressive load which tends to shorten itthereby expanding or mushrooming the diameter.

The pressurized fluid in the first and second pressure chambers 237 and247 also reduces friction between the first stepped piston 234 and endrestraining member 215, and between the second stepped piston 241 andend restraining member 216. If the pressure Within the second annularpressure chamber 247 exceeds a predetermined value, high-pressure fluidvents past the seal 246 to the atmosphere. However, under normaloperating conditions this does not occur.

As the pressure in the first annular pressure chamber 237 increases, theupper end restraining member 215 elastically expands permitting fluid toescape past the seal 239, through the radial aperture 225 and into theenclosed annular space 223 between the casing 222 and the intermediatecylinder 221. The pressurized fluid within the enclosed annular space223 acts against the intermediate eylindcr 221. which in turn forces thesegmented cylinder 211 inwardly to support the forming cylinder 202during the forming operation.

Continued movement of the pistons 234 and 241 increases the pressure ofthe fluid acting against the metal blank 100 until the blank 100 isdrawn and extruded through the forming die 107 as described in the FirstEmbodiment.

ALTERNATIVE EMBODIMENT Referring now to FIG. 5, there is shown analternative embodiment of a high-pressure forming apparatus for forminga metal blank 100 into a tubular cup-shaped member 101. The alternativeembodiment is similar in many respects to the first embodiment which isdescribed in great detail. Accordingly, the detailed descriptions of thesimilar features are not repeated in the following description, andreference may be made to the description of the first embodiment formore complete details. The alternative embodiment high-pressureapparatus includes a forming cylinder 301 with a bore 332 therethroughwhich is filled with fluid during the forming operation. The formingcylinder 301 has an upper beveled surface 303 and a lower beveledsurface 304. A drawing and extrusion die, generally designated as 600(see FIG. 11) having a metal blank 100 secured therein is positionedwithin the bore 392 of the forming cylinder 301. The die 600 isdescribed in greater detail further on under the heading AlternativeDie.

A hollow segmented cylinder 306, having an upper conically-shapedcounterbore 337 and a lower conicallyshaped counterbore 308, surroundsthe forming cylinder 331. An upper conically-shaped hollow endrestraining member 309 fits within the counterbore 307 and has a beveledsurface 311 abutting against the beveled surface 303 of the formingcylinder 301 to provide support thereto. A lower externally threadedconically-shaped hollow end restraining member 312 fits within thecounterbore 393 and has a beveled surface 313 abutting against the lowerbeveled surface 304 of the forming cylinder 301 to provide supportthereto. A hollow intermediate cylinder 314 tightly surrounds thesegmented cylinder 306 and has upper and lower conical surfaces injuxtaposition with the upper and lower end restraining members 309 and312.

A casing 316 surrounds and is spaced from the intermediate cylinder 314to provide an annular space 317 therebetween for receiving fluid. Thecasing 316 has a lower internally threaded portion 318 which cooperateswith the threads on the lower end restraining member 312. The casing 316has a groove 319 therein for receiving an annular seal 321 toeffectively enclose the bottom of the annular space 317. Casing 316 hasan upper threaded portion 322 for receiving an externally threadedsupport ring 323 which has a lower surface 324 in juxtaposition with theupper surface of the end restraining member 309.

The end restraining member 309 has an aperture 325 therethrough whichpermits fluid under pressure to pass from the bore 302 of the formingcylinder 301 into the annular space 317. As shown in FIG. 6, the supportring 323 has a groove 326 therein for receiving an annular seal 327which prevents pressurized fluid in space 317 from escaping between thesupport ring 323 and the end restrainin member 309. Another annular seal328 is positioned below the support ring 323 to prevent highpressurefluid from escaping out the top of annular space 317. An annular seal330 is positioned between end restraining member 309, intermediatecylinder 314, and casing 316 to prevent high-pressure fluid fromentering the space between the segments of cylinder 306. However, ifpressurized fluid leaks past the seal 330, the end restraining member309 is provided with a plurality of equally-spaced passageways 329 whichvent fluid trapped between the segments of the cylinder 306 toatmosphere.

A first high-pressure piston 331 is slidably mounted within the bore 302of the forming cylinder 301 and is movable by a high-pressure ram 332which could be part of a conventional high-pressure press. Piston 331has a limited diameter seal 335 attached to the end thereof. A secondpiston 333 is slidably mounted for movement within the bore 302 opposingthe first highpressure piston 331. Piston 333 has a limited diameterseal 336 attached to the end thereof. The second piston 333 isindependently driven by a ram 34 which could also be part of aconventional high-pressure press. The seals 335 and 336 aresubstantially similar to the limited diameter seal shown in FIG. 3. Theapparatus includes an over-balance valve, not shown, similar to valve148 shown in FIG. 1, to vent fluid from the annular space 317.

OPERATION In operation, the first piston 331 is withdrawn and bore 302of forming cylinder 301 is filled with hydraulic fluid. Then the drawingand extrusion die 600, with a metal blank secured therein, is insertedinto the fluid-filled bore 302.

Next, the first piston 331 and the second piston 333 are actuated tomove toward the drawing and extruding die 600. As pressure builds upwithin the upper part of the forming cylinder 301 (the part above thedie 600). the cylinder 301 is strained until it elastically expands,allowing high-pressure fluid to escape past the seal 335 and through theaperture 325 of the upper end restraining member 309 into the annularspace 317 between the easing 316 and the intermediate cylinder 314. Thepressurized fluid within the annular space 317 acts on the intermediatecylinder 314 which in turn forces the segmented cylinder 306 inwardly tosupport the forming cylinder 301, thereby decreasing the net pressureacross the wall of the forming cylinder. In addition, pressurized fluidtrapped between the lower surface 324 of the threaded support ring 323and the upper surface of end restraining member 309, acts on the endrestraining memher 309 forcing it inwardly and downwardly (as shown inFIG. 6) to counteract the radial and the longitudinal (pinch-off) forcesgenerated in the forming cylinder 301. As the pressure continues toincrease in the forming cylinder 301, the pressure also increases inannular space 317, thereby providing increasing forces against both theend restraining member 309 and the intermediate cylinder 314. The ventpassageways 329 in the upper end restraining member 309 provide anescape to the atmosphere for any fluid which leaks into the spacesbetween the segments of the cylinder 306. Such fluid is forced out thevent passageways 329 when the segments of cylinder 306 are forcedinwardly.

As the pistons 331 and 333 continue further movement, the pressurewithin the forming cylinder 301 increases until the blank is drawn andextruded into a tubular cup-shaped member 101. During the movement ofthe pistons toward each other, the wall of the forming cylinder 301expands under the high internal pressure and contracts under thesupporting pressures many times, as previously described, until thenecessary drawing and extruding pressure is attained within the formingcylinder 301.

ALTERNATEVE EMBODIMENT Referring now to FIG. 7, there is shown analternative embodiment of a high-pressure forming apparatus for forminga metal blank 100 into a tubular cup-shaped member 131. The alternativeembodiment is similar in many respects to the first embodiment which isdescribed in great detail. Accordingly, repetitious description ofsimilar or identical elements are not included in the followingdescription, and for further details reference should be made to thedescription of the first embodiment. The alternative embodiment includesa hollow forming cylinder 401 having a top flanged portion 402 which hasa bore 407 therethrough for receiving the first step 438 of amulti-stepped piston 409. An inner cylinder 403 is tightly fitted withinthe bottom of forming cylinder 401 and has a bore 404 therethrough forreceiving a piston 496. Step 408 of piston 469 is encompassed by awear-resistant sleeve 411 which is shorter than the length of the firststep 408. The outer diameter of the wearresistant sleeve 411 issubstantially equal to the diameter of the bore 407.

A second hollow cylinder 413 surrounds and is spaced from the formingcylinder 4E1 to provide an annular space 414 therebetween. The secondcylinder 413 has a bottom flanged portion 416 which is threaded orforcefitted against the periphery of the forming cylinder 431 to enclosethe bottom of the annular space 414. The second cylinder 413 has a topflanged portion 417 having a bore 418 therethrough for receiving thesecond step 419 of the stepped piston 409. A wear-resistant sleeve 421encompasses the second step 419 of piston 469. Sleeve 421 has anaperture 422 through the bottom thereof which is slightly larger thanthe outer diameter of sleeve 411.

A third hollow cylinder 423 surrounds and is spaced from the secondcylinder 413 to provide an annular space 424 therebetwcen. The thirdcylinder 423 has a bottom flanged portion 426 which is threaded orforce-fitted against the outer periphery of the second cylinder 413 toeffectively enclose the bottom of annular space 424. The third cylinder423 has a flanged top portion 428 having a bore 429 theret'nrough forreceiving the third step 431 of the piston 409. A wear-resistant sleeve432 encompasses the third step 431 of piston 469 Sleeve 432 has anaperture 439 through the bottom thereof which is sli htly larger thanthe outer diameter of sleeve 421.

The top flanged portions 402, 417, and 428 of cylinders 4G1, 413, and423, respectively, are provided so that pressurized fluid actinthereagainst generates longitudinal forces downwardly (see FIG. 8) tocounteract the longitudinal or pinch-off forces which are generated inthe walls of the cylinders by the high opposing radial forces actingthereon.

A casing 433 surrounds and is spaced from the third cylinder 423 toprovide an enclosed space 434 therebetween. The casing 433 has a bore435 therethrough for receiving the fourth step 437 of piston 499 whichis encompassed by a wear-resistant sleeve 438. The sleeve 438 has anaperture 440 through the bottom thereof which is slightly larger thanthe outer diameter of sleeve 432.

The wear-resistant sleeves 419, 421, 432, and 438 are made of amaterial, such as chrome plated high carbon steel, which has very goodwear characteristics. Each sleeve has an aperture through the bottomthereof which is sufiiciently large to pass over the preceding step andsleeve. This permits any sleeve to be individually and easily replacedwhen it becomes worn. Furthermore, the replaceable feature of thesleeves prolongs the useful life of the stepped piston and cylinders. Inaddition, each wear-resistant sleeve is shorter than the length of thestep which it encompasses to permit pressurized fluid to act axiallyagainst the edge of the sleeve.

Moreover, the depth of each cylinder is slightly greater than the lengthof each wear-resistant sleeve so that the sleeve may slide off thepiston into the cylinder to provide a fluid passageway such as 436, asshown in FIG. 9, between the cylinder and the surrounding annular space.

OPERATION In operation, the stepped piston 4%? is withdrawn, a metalblank 13s is secured between the ring 198 and the die 107, and theforming cylinder 4&1 is filled with hydraulic fluid. Piston tdandstepped piston 339 are then independently moved toward each other. Asthe pressure increases, forming cylinder 401 is strained and elasticallyexpands allowing fluid to pass between the first wearresistant sleeve411 and the top flanged portion into the annular space 414. As thestepped piston 409 moves downwardly, the pressure within annular space414 increases until the second cylinder 413 is strained sufficiently andelastically expands allowing fiuid to pass into the annular space 424.Further downward movement of the 1.2 stepped piston 409 strains thethird cylinder .23 so that fluid passes into the annular space 434. Eachsuccessive cylinder is supported by the pressurized fluid in thesurrounding annular space.

Referring now to FIG. 8, there is shown an enlarged view taken from FIG.7 of one wear-resistant sleeve and the forces acting thereon. Thepressure within the forming cylinder 401 is denoted as P1. The pressurewithin the annular space 414 is denoted as P2. Pressure P1 acts upwardlyforcing the sleeve 411 against the bottom of first step 408 of piston409. In addition, pressure P1 also acts radially, forcing the portion ofsleeve 411, which is in cylinder 4%, inwardly against the step 4-08 ofpiston 499. The upper portion of the sleeve 41-1 is subjected to radialpressure P2 acting inwardly to force the sleeve 411 against the step408. There is also an axial force from pressure P2 acting against theedge of sleeve 411 which tends to push sleeve 4-11 downwardly into theforming chamber 401. But, since pressure P1 is greater than pressure P2,the axial force of P2 is effectively opposed and the sleeve 411 remainsin contact with the piston 409. However, if pressure Pl dropssubstantially below pressure P2, the sleeve 411 is forced downwardlyinto the forming cylinder 481 thereby providing a fluid passageway 436(as shown in FIG. 9) between annular space 414- and forming cylinder 401which allows equalization of the pressures (P1 and P2) therebetween. Ifthere is no sleeve on the piston or if the sleeve is not movable, a lossof pressure in cylinder 461 results in an unopposed high pressure actinginwardly which may be great enough to rupture or produce failure incylinder 401. The wearresistant sleeves prevent this occurrence byeffectively acting as pressure-relief valves between successivecylinders.

In normal operation, the stepped piston continues downwardly untilsulficient pressure is attained within the forming cylinder 401 to drawand extrude the metal blank into a tubular cup-shaped article 161.

ALTERNATIVE EMBODIMENT Referring now to FIG. 10, there is shown analternative embodiment of a high-pressure forming apparatus for forminga metal blank 10%) into a tubular cup-shaped member 101 (as shown by thedotted lines). The alternative embodiment is similar in many respects tothe first embodiment, which is described in great detail. Accordingly,the detailed description of similar features are not repeated in thefollowing description, and reference should be made to the descriptionof the first embodiment for more complete details. The alternativehigh-pressure apparatus includes a movable forming cylinder 502 having abore 503 partially therethrough and a counterbore 504- through one endthereof. A radial aperture 506 extends through the wall of the movableforming cylinder 5632 into bore 563. The forming cylinder 502 has ashoulder 507 formed by the juncture of the bore 503 and the counterbore504. A forming die "508 is mounted within counterbore 504 in abuttingrelationship with the shoulder 507. A threaded ring 509 having grooves511 extending axially through its threads fixedly holds a metal blank 1%against the forming die 5%.

A first cup-shaped cylinder 512 having a tapered top portion and anaperture 513 through its bottom surrounds and is spaced from the movablecylinder 502. A stationary piston 514 having an intermediate taperedportion 516 is force-fitted into the aperture 513 of cylinder 512.Aperture 513 is countersunk from both ends thereof to provide onlyminimum contact with tapered portion 516. The end of stationary piston514 extends upward into the counterbore 504 and has a limited diameterseal 517 attached thereto (similar to the seal shown in FIG. 3). Anannular seal 518 is held in position by a threaded ring 519 to providean enclosed annular space 521 between cylinder 512 and cylinder 502. Asecond cup-shaped cylinder 522 surrounds and encloses the firstcup-shaped cylinder 512 to provide an enclosed annular space 523 there-13 between. A third cup-shaped cylinder 524 surrounds the secondcup-shaped cylinder 522 to provide an enclosed annular space 526therebetween. A casing 527 surrounds the third cup-shaped cylinder 524to provide an enclosed annular space 52-8 therebetween.

OPERATION In operation, the movable forming cylinder 502 is completelywithdrawn and hydraulic fluid is introduced into the first cup-shapedcylinder 512. The forming dies 508 is inserted into counterbore 504 andthe metal blank 100 is fixedly positioned thereagainst by the threadedring 509. The forming cylinder 502 is then moved into the cupshapedcylinder 512 so that the bore 503 and the counterbore 504 fill withfluid.

As the cylinder 502 moves downwardly, the pressure of the fluid incylinder 512 increases. In addition, the pressure of the fluid withinthe counterbore 504 increases until the forming cylinder 502 issufliciently strained to elastically expand allowing fluid to escapepast the limited diameter seal 517 into the enclosed space 521.

The pressurized fluid contained within the enclosed space 521 passesthrough the radial aperture 506 into the bore 503 of the movable formingcylinder 502 to provide a back-up pressure against the metal blank 100.This backup pressure is substantially lower than the pressure within thecounterbore 504, but is sufficiently high to increase the ductility ofthe metal blank 100.

The pressurized fluid within the enclosed space 521 exerts an inwardpressure on the movable forming cylinder 502 counteracting the pressurewithin the counterbore 504 so that the forming cylinder 502 contractsand cuts off the flow o-f fluid past the limited diameter seal 517. Asthe movable forming cylinder 502 continues downwardly, the pressure inthe enclosed annular space 521 increases until the first cup-shapedcylinder 512 is strained sufficiently to elastically expand. At thistime, pressurzied fluid passes between the first cup-shaped cylinder 512and the tapered portion 516 of stationary piston 514 into the enclosedannular space 523. Then the pres- 1 surized fluid within the enclosedannular space 523 acts on the first cup shaped cylinder 512 forcing itinwardly against the tapered portion 516, thereby counteracting thepressure of the fluid in enclosed space 521.

As the movable forming cylinder 502 continues downwardly, the pressureof the fluid within the enclosed annular space 523 increases and strainsthe second cupshaped cylinder 522 until it elastically expands allowingfluid to pass into the enclosed annular space 526. As the pressureincreases within the enclosed annular space 526-, the third cup-shapedcylinder 524 is strained and elastically expands allowing fluid to passbetween the third cup-shaped cylinder 524 and the tapered top portion ofthe first cup shaped cylinder 512 into the annular space 528. If apredetermined pressure is reached within annular space 528, the casing526 expands allowing fluid to vent to the atmosphere to prevent overloadof the apparatus. However, this predetermined pressure is not normallyattained during operation of the apparatus.

Cylinder 502 moves downwardly until the pressure within counterbore 504is sufficiently high to draw and extrude the metal blank 100 through theforming die 508.

The enclosed annular spaces 521, 523, 526, and 528 contain fluid ofsuccessively decreasing pressures which are utilized to counteract thepressures in the forming cylinder 502. Hence, ultra-high formingpressures can be generated within the counterbore 504 without rupture orfailure of the forming cylinder 502.

ALTERNATIVE DIE Referring now to FIG. 11, there is shown an alternativedrawing and extrusion die 600 which can be used with any embodiment ofthe high-pressure metal forming apparatus shown in the precedingdrawings. The drawing and extrusion die 600 includes a cylindrical upperdie member 601 having a bore 602 therethrough for receiving a draw punch617. Die member 601 has an internally threaded counterbore 603 with aplurality of axially extending grooves 605 formed in the threadedsurface.

A cylindrical lower die member 604 is externally threaded to engage withthe internal threads in counterbore 603 of the upper die member 601 tosecure a metal blank 100 the-rebetween. The metal blank 100 is slightlysmaller in diameter than the counterbore 603 so that an annular space613 is defined between the periphery of the metal blank 100 and thecounterbore 603. The lower die member 604 has a plurality of axiallyextending grooves 612 formed in the threaded surface comunicating withthe annular space 613. Grooves 605 may be unnecessary providing grooves612 are deeper than the threads of the lower die member 604. The lowerdie member 604 has an axial bore 606 therethrough aligned with the bore602 of the upper die member 601. An annular bore 607 for receiving ahollow cup-shaped piston 609, extends partially upward from the bottomof the lower die member 604, concentric with the axial bore 607. Anannular counterbore 610 in the lower die member 604 receives annularseals 618 and 619 and seal retainers 620 and 621 to eflectively preventhigh-pressure fluid contained within the anular bore 607 from escapingpast the hollow piston 609. A plurality of radial apertures 608 connectthe annular bore 607 with the axially extending grooves 605 and 612 inthe threads of the upper and lower die members 601 and 604. Seals 622and 623 are provided to prevent fluid from passing between the formingcylinder 614 and the upper and lower die members 601 and 604.

OPERATION In operation, a cylindrical metal blank 10 is placed betweenthe upper die member 601 and the lower die member 604 and the diemembers are threaded securely together. The die members and the metalblank are then completely immersed in a fluid-filled forming cylinder614. The draw punch 617 is inserted into bore 602 of the upper diemember 601 and abuts against the upper face of the metal blank 100.

A first piston 616 and a second piston 611 are independently movedtoward each other, by facilities such as the rams of conventionalhigh-pressure hydraulic presses, to increase the pressure within theforming cylinder 614. The pressure of the fluid in the enclosed spacebetween the first piston 616 and the upper die member 601 willhereinafter be referred to as P1. The pressure of the fluid in theenclosed space between the second piston 611 and the lower die member604- will hereinafter be referred to as P2. The pressure of the fluidwithin the annular bore 607 will hereinafter be referred to as P3.Pressures P1, P2 and P3 are equal until the hollow cup-shaped piston 609enters the fluid-filled annular bore 607. At this time, the pressure P3increases and the pressurized fluid passes through the aperture 608 andgrooves 605 and 612 to act against the peripheral edge of the metalblank 100. The high pressure P3 generated by the piston 609 tends toextrude the metal blank through the axial bore 606 of the lower diemember 604. As pressure P3 rises, pressure P1 rises and becomes largerthan pressure P2 thus providing a pressure diflerential of Pit-P2 acrossthe metal lank 100. However, pressure P2 is still suificiently high toincrease the ductility of the metal blank 100. Any increase in pressureP2 over a predetermined value will expand the wall of the formingcylinder 614 and allow fluid to vent past piston 611 to the atmosphere.The draw punch 617 tends to force the metal blank 100 down into thelower die member 604 while the fluid in the annular space 613 underpressure P3 simultaneously acts on the periphery of the blank 100. Thecombination of pressures P1 and P3 draw and extrude the 'metal blank 100into a tubular cup-shaped article 101. By balancing the extrusionpressure P3 and the drawing punch pressure P1, very deep cup-shapedarticles can be formed.

The forming cylinder 614 is supported against the high pressuresgenerated within by utilizing the elastic deformation of the formingcylinder to vent support fluid to an enclosed annular space surroundingthe forming cylinder as hereinbefore described.

It is to be understood that the above-described embodiments of theinvention are merely illustrative and that numerous modifications may bemade within the spirit and scope of the invention.

What is claimed is:

1. A high-pressure press comprising:

an expandable hollow cylinder closed at one end for receiving fluid,

a piston movable within said cylinder,

means for moving said piston with sufficient force to pressurize saidfluid sufliciently to expand the wall of said cylinder away from saidpiston to pass fluid out of said cylinder between said cylinder and saidpiston, and

casing means, providing an enclosed space around said cylinder forreceiving the passed fluid.

2. A pressure vessel comprising:

a cylinder having an axial bore through one end for receiving fluid,said cylinder constructed to elastically expand upon the received fluidbeing pressurized to a predetermined pressure,

a piston movable within the bore of said cylinder to pressurize saidfluid,

means for moving said piston against said fluid with suflicient force togenerate said predetermined pressure to radially expand said cylinderaway from said piston to provide a fluid passageway through which thepressurized fluid can be forced, and

easing means spaced from the surrounding said cylinder for receivingsaid pressurized fluid forced through said passageway and confining saidpressurized fluid to exert inward supporting forces against saidcylinder.

3. A high-pressure press comprising:

a casing,

an expandable hollow cylinder closed at one end for receiving fluidmounted within and spaced from said casing,

a piston mounted for movement within said cylinder,

means for sealing said casing to said piston to provide an confinedspace between said casing and said cylinder, and

means for moving said piston within said cylinder with sutficient forceto act on and force the fluid to expand said cylinder and pass fluidbetween said piston and said cylinder into said confined space togenerate fluid forces to act inwardly against said cylinder.

. A pressure vessel, comprising:

a series of concentrically spaced hollow cylinders for receiving fluid,said cylinders constructed to elastically expand upon subjection topredetermined internal pressures,

means for sequentially generating said predetermined pressures withinsaid cylinders from the innermost cylinder successively outwardly toexpand each succeeding cylinder to pass fluid to the surroundingcylinder, and

means for confining said fluid between said cylinders to counteract thepressures within the inner cylinders by the pressures within eachsucceeding outer cylinder.

5. A pressure vessel, comprising:

a series of concentrically spaced hollow cylinders for receiving fluid,said cylinders constructed to elastically expand upon subjection topredetermined internal pressures,

means for sequentially generating said predetermined pressures withinsaid cylinders from the innermost cylinders successively outwardly toradially expand each succeeding cylinder to pass fluid to thesurrounding cylinder,

means for confining said fluid between said cylinders within theinnermost cylinders by the pressures within each succeeding outercylinder, and

means responsive to the generation of said predetermined pressures forgenerating longitudinal forces against said cylinders to counteract thelongitudinal forces generated by the opposing radial pressures acting oneach succeeding cylinder.

6. In an ultra-high pressure forming apparatus:

a series of concentrically spaced hollow cylinders for receiving fluid,said cylinders constructed to elastically expand upon subjection topredetermined internal pressures,

means for sequentially generating said predetermined pressures withinsaid cylinders from the innermost cylinder successively outwardly toradially expand each succeeding cylinder to pass fluid to thesurrounding cylinder,

means for confining said fluid between said cylinders to counteract thepressures within the inner cylinders by the pressure within eachsucceeding outer cylinder, and

means responsive to a decrease in pressure in the innermost cylinder forequalizing the pressures in succeeding cylinders.

7. In an ultra-high pressure forming apparatus:

a series of concentrically spaced hollow cylinders for receiving fluid,said cylinders constructed of material that elastically expands uponsubjection to predetermined internal pressures,

means for generating said predetermined pressures within said cylindersfrom the innermost cylinder successively outwardly to radially expandeach succeeding cylinder to pass fluid to the surrounding cylinder,

means for confining said fluid between said cylinders to counteract thepressures within the inner cylinders by the decreasing pressures withineach succeeding outer cylinder,

means responsive to the generation of said predetermined pressures forgenerating longitudinal forces against said cylinders to counteract thelongitudinal forces generated by the opposing radial pressures acting oneach succeeding cylinder, and

pressure relief means actuated by the reversal in pressure differentialwithin an inner cylinder and the next succeeding outer cylinder forreducing said pressure differential.

8. A pressure vessel, comprising:

a forming cylinder having an axial bore through one end for receivingfluid, said cylinder constructed to elastically expand upon subjectionto a predetermined internal pressure,

a piston movable within the bore of said cylinder,

means for moving said piston against said fluid with sufficient force togenerate said predetermined pressure in said bore to radially expandsaid cylinder away from said piston to provide a fluid passageway,

a casing spaced from and surrounding said cylinder to provide a confinedspace for receiving said fluid forced through said passageway whichconfined fluid provides support to said forming cylinder, and

means mounted on said piston and moved in response to a decrease inpressure within said bore for equalizing the pressures within saidforming cylinder and said casing.

9. A metal forming press comprising:

an expandable hollow cylinder closed at one end for receiving fluid andhaving an inwardly formed flange on the other end to provide an aperturetherethrough,

a piston movable within said aperture,

a cup-shaped sleeve movably mounted on said piston and having a lengthless than the distance from the bottom of the flange to the bottom ofthe cylinder,

means for moving said piston with suflicient force to radially expandsaid hollow cylinder to pass fluid between said flange and said sleeve,and

a casing surrounding said cylinder and engaging said piston forreceiving said passed fluid to support said cylinder and to apply aforce to move said cupshaped sleeve into said cylinder in response to adecrease in the pressure of the fluid within said cylinder whereby afluid passageway is provided between said piston and said flange forequalizing the pressures within said casing and said cylinder.

10. In a high-pressure press:

an elastically expandable forming cylinder having a bore through one endthereof for receiving fluid,

a piston mounted for movement in said bore,

casing means surrounding said forming cylinder and engaging said pistonto provide a confined space between said forming cylinder and saidcasing,

means for moving said piston with sufiicient force to increase thepressure of the fluid in said bore to elastically expand said formingcylinder to pass fluid into said confined space to support said formingcylinder, and

a cup-shaped sleeve movably mounted on the end of said piston and havinga length less than the depth of said bore, said sleeve having the upperend thereof exposed to the fluid within said confined space and havingforces acting thereon to move said sleeve into said forming cylinder inresponse to a decrease in pressure in said bore.

11. A high-pressure press comprising:

a casing,

a hollow cylinder closed at one end for receiving fluid mounted withinand spaced from, said casing,

a piston mounted for movement within said cylinder,

means for sealing said casing to said piston to provide a confined spacebetween said casing and said cylinder,

means for moving said piston with suflicient force to increase thepressure of said fluid within said cylinder and elastically expand saidcylinder to pass fluid between said piston and said cylinder into saidconfined space wherein said fluid generates radial forces actinginwardly against said cylinder to oppose the outwardly acting radialforces within said cylinder, whereupon said opposing inward and outwardradial forces generate longitudinal pinch-off forces in said cylinder,and

means responsive to said forces generated within said confined space foropposing said longitudinal forces.

12. In a high-pressure press:

a cylinder having a bore extending therein for receiving fluid,

a casing surrounding said cylinder to provide a confined spacetherebetween,

said cylinder having a passageway communicating said bore with saidconfined space,

a piston movably mounted within said bore to cover said passageway,

means for moving said piston within said bore with sufiicient force toincrease the pressure of the fluid therein to elastically expand saidcylinder to pass fluid between said piston and said cylinder throughsaid passageway into said confined space to generate forces thereinwhich act inwardly to support said cylinder, whereupon said inwardforces act in conjunction with the outward forces generated within thebore to generate longitudinally extending pinchoff forces in saidcylinder, and

means responsive to the forces generated in said confined space forapplying forces to said cylinder to oppose the longitudinally extendingpinch-oif forces.

13. A high-pressure press comprising:

a hollow cylinder for receiving fluid,

a first piston mounted for movement within said cylinder,

a second piston mounted for movement within said cylinder opposing saidfirst piston,

means for moving said first piston and said second piston relative toeach other with sufiicient force to increase the pressure of said fluidto elastically expand said cylinder and provide a fluid passagewaybetween said cylinder and said pistons, and

easing means surrounding said cylinder to provide an enclosed spacetherebetween for receiving the fluid passing through said passageway.

14. A high-pressure metal forming press comprising:

a hollow cylinder for receiving fluid,

-a die having an orifice therethrough mounted within said cylinder forreceiving a metal blank thereon,

a first piston mounted for movement within one end of said cylinder,

a second piston mounted for movement within the other end of saidcylinder opposing said first piston, means for moving said second pistonwith suflicient force to increase the pressure of the fluid to apredetermined value to increase the ductility of said metal blank,

means for moving said first piston with sufficient force to increase thepressure of said fluid to (a) elastically expand said cylinder to passfluid between said first piston and said cylinder and (b) draw saidmetal blank through said die, and

a casing surrounding said cylinder to provide an enclosed spacetherebetween for receiving the fluid passing from said cylinder.

15. A pressure vessel, comprising:

a casing,

a hollow intermediate cylinder mounted within and spaced from saidcasing,

means for sealing the ends of said casing to the ends of saidintermediate cylinder to provide an enclosed annular space therebetween,

a segmented cylinder having a bore therethrough mounted within saidintermediate cylinder,

said segmented cylinder having an upper threaded coun-terbore,

an elastically expandable forming cylinder mounted within the bore ofsaid segmented cylinder having a bore extending from the top thereof forreceiving fluid,

said forming cylinder having a beveled top surface,

a hollow end restraining member threaded into said upper counterbore ofsaid segmented cylinder having a beveled bottom surface abutting againstthe beveled top surface of said forming cylinder, said end restrainingmember having an internal bottom section extending inwardly to thediameter of the bore of said forming cylinder,

said end restraining member, segmented cylinder and intermediatecylinder having a radial passageway therethrough communicating theinternal surface of said upper end restraining member with said enclosedannular space,

a stepped piston having a first diameter portion movable within saidbore of said forming cylinder and a second diameter portion movableWithin said end restraining member to cover said radial passageway andprovide an annular pressure chamber between said end restraining memberand said first diameter portion of said stepped piston, and

means for moving said stepped piston with suflicient force to increasethe pressure of the fluid in said bore of said forming cylinder toelastically expand said forming cylinder to pass fluid into said annularpressure chamber to radially support said first diameter portion, saidmoving means increasing the pressure in said annular pressure chamber toelastically expand said end restraining member to pass fluid 19 throughsaid radial aperture into said enclosed annular space.

16. A pressure vessel, comprising:

an elastically expandable hollow cylinder for receiving fluid,

a first piston spaced from and movable within an end of said cylinder,said piston having a recess extending from one end for receiving fluid,

a seal between said first piston and the top of said cylinder,

a stepped piston having a first diameter section force fitted within theother end of said cylinder and a second diameter section projectingwithin said recess,

means for moving said first piston with suflicient force to act on thefluid (a) within said recess to elastically expand said first piston topass fluid between said first pis ton and said second section of saidstepped piston into the space between said first piston and saidcylinder and (b) within said space to elastically expand said cylinderto pass fluid between said cylinder and said first section of saidstepped piston, and

a casing surounding said cylinder to provide an enclosed space forreceiving fluid passing between said cylinder and said first section ofsaid stepped piston and confining said fluid to exert inward supportingforces against said cylinder.

17. A high-pressure press comprising:

an elastically expandable forming cylinder having a bore through one endthereof for receiving fluid, said cylinder having a top beveled surface,

a cylinder divided into segments surrounding said forming cylinder, saidsegmented cylinder having an axial bore therethrough with a threadedupper portion therein and a radial aperture extending into said threadedportion,

an end restraining member threaded into said upper portion of saidsegmented cylinder and having a lower beveled surface in juxtapositionwith said top beveled surface of said cylinder, said member having anaxial bore therethrough in alignment with said bore of said formingcylinder and having a radial aperture extending therethrough inalignment with the radial aperture in said segmented cylinder,

a hollow intermediate cylinder surounding said segmented cylinder andhaving a radial aperture therethrough in alignment with the radialaperture in said segmented cylinder,

a casing spaced from and surrounding said intermediate cylinder,

means for sealing said casing to said intermediate cylinder to providean enclosed annular space therebetween,

a piston movable within said bore of said forming cylinder, and

means for moving said piston with sufficient force to increase thepressure of the fluid in said bore to elastically expand said formingcylinder to pass fluid between said piston and said cylinder, throughsaid radial apertures into said enclosed space to generate fluid forcesacting inwardly to support said forming cylinder.

18. A pressure vessel, comprising:

a casing,

an intermediate cylinder mounted within and spaced from said casing,

means for sealing said intermediate cylinder to said casing to providean enclosed space therebetween,

a hollow segmented cylinder mounted within said intermediate cylinderand having an upper internally threaded portion,

an elastically expandable forming cylinder mounted within said segmentedcylinder, said forming cylinder having a bore through one end thereoffor receiving fluid and having a beveled top surface, an end restrainingmember having external threads thereon for cooperating with said upperthreaded portion of said segmented cylinder, said external threadshaving a predetermined greater pitch than the threads of said segmentedcylinder for uniformly distributing the load on the threads during theforming operation, said end restraining member having (a) a lowerbeveled surface in juxtaposition with said beveled top surface of saidforming cylinder, and (b) a bore therethrough in alignment with saidbore of said forming cylinder, a piston mounted for movement within saidbore of said forming cylinder, said end restraining member, segmentedcylinder and intermediate cylinder having aligned radial passagewaysextending therethrough into said enclosed space, and means for movingsaid piston with suflicient force to increase the pressure of the fluidto elastically expand said forming cylinder to pass fluid between saidpiston and said forming cylinder through said radial passageway intosaid enclosed space, wherein the fluid exerts inward forces to supportsaid forming cylinder. 19. In a press for forming metal blanks underultrahigh fluid pressure:

a forming cylinder having a bore therethrough for receiving fluid,

a die member having an orifice therethrough mounted within said bore forsupporting a circular metal blank having a diameter smaller than thediameter of said bore to provide an annular space between said blank andsaid forming cylinder for receiving fluid,

a ring member mounted within said bore to hold said blank against saiddie, said ring member having axial grooves in the periphery thereof topass fluid into said annular space to act against the periphery of saidblank,

means for increasing the pressure of the fluid acting on the bottom ofsaid blank to a predetermined value to increase the ductility of saidblank,

means for increasing the pressure of the fluid acting against theperiphery and the top of said metal blank to elastically expand saidcylinder to pass fluid therefrom and to force said blank through theorifice of said die member, and

means for confining said escaping fluid to exert inward supportingforces against said cylinder.

20. In a high-pressure forming press:

an elastically expandable forming cylinder having a bore through one endthereof for receiving fluid,

a piston mounted for movement in said bore,

a seal attached to the end of said piston,

casing means surrounding said forming cylinder and engaging said pistonto provide an enclosed space between said forming cylinder and saidcasing,

means for moving said piston with suflicient force to increase thepressure of the fluid within said bore to elastically expand saidforming cylinder away from said seal and pass fluid into said enclosedspace to generate support forces acting inwardly against said formingcylinder, and

means for limiting the diametrical expansion of said seal with respectto said cylinder.

21. In a high-pressure press:

a cylinder having an axial bore through one end for receiving fluid,said cylinder constructed to elastically expand upon subjection to apredetermined pressure,

a piston movable within said bore of said cylinder,

a seal assembly attached to the end of said piston to retain fluidwithin said bore, said seal including an expandable beveled edged memberand a limiter disc having an axially extending beveled flange on theperiphery thereof partially surrounding said expandable member to limitthe diametrical expansion of said member,

means for moving said piston with suflicient force to generate saidpredetermined pressure to expand said cylinder away from said seal toprovide a fluid passageway therebetween, and

a casing spaced from and surrounding said cylinder for receiving thefluid passing through said passageway and confining said fluid to exertinward supporting forces against said cylinder.

22. In a high-pressure forming press:

a fluid-filled forming cylinder having a beveled end,

an array of segmented sections surrounding said cylinder, having afrusto-conical recess formed in one end thereof,

double-walled casing means surrounding said segments,

a hollow conical plug secured to said casing means and extending intosaid frusto-conical recess, said plug having a conical recess formed inthe end thereof to accommodate the beveled end of said cylinder,

a piston mounted for movement within said cylinder,

means for moving the piston within said cylinder to force the fluid toelastically expand the cylinder wall and pass fluid between said pistonand cylinder, and

said plug having a passageway therethrough to conduct said passed fluidto said casing means whereupon said passed fluid acts against said plugand segments.

23. In a high-pressure press:

a fluid-filled forming cylinder having a beveled end,

casing means surrounding and spaced from said cylinder and having aninwardly projecting flange,

said flange having an inner surface beveled toward the inner wall ofsaid casing,

an end restraining member interposed between said beveled end and saidbeveled flange surface,

a piston mounted for movement in said cylinder,

means for moving said piston to increase the pressure of said fluid toelastically expand said forming cylinder to pass the fluid between thepiston and the cylinder wall,

said end restraining member having a passageway therethrough forconducting said passed fluid to the juncture of said beveled flange andsaid end restraining member, whereupon said passed fluid forces the endrestraining member against the beveled end of said cylinder, and

means responsive to the fluid passed through said juncture for applyingforces against said forming cylinder;

24. A pressure vessel comprising:

expandable means for providing a first fluid chamber for receiving fluidto be pressurized;

means for providing a second fluid chamber around said expandable means;

means for pressurizing fluid in said first fluid chamber;

said expandable means, in response to pressurized fluid receivedtherein, being expandable to communicate said first fluid chamber withsaid second fluid chamber to permit a portion of the pressurized fluidreceived in said first chamber to pass into said second chamber andprovide support to said expandable means.

25. A pressure vessel, comprising:

expandable means for providing a first fluid chamber for containingpressurized fluid;

means for providing a second fluid chamber surrounding said expandablemeans and for containing fluid for providing support to said expandablemeans;

said expandable means, upon the occurrence of a predetermined pressurediflerential between the pressurized fluid in the first chamber and thepressurized fluid in the second chamber, being expandable to communicatesaid chambers to relieve a portion of the pressurized fluid from saidfirst chamber into said second chamber whereupon said relievedpressurized fluid further supports said expandable means in containingthe pressurized fluid contained in said first chamber.

References Cited UNITED STATES PATENTS 316,967 5/1885 Heber 138148667,525 2/1901 Huber 7260 2,558,035 6/1951 Bridgman 726O 2,937,6065/1960 Paulton 7257 3,030,776 4/1962 Kustusch 6054.5 3,060,507 10/1962Knowles 726O 3,099,993 8/1963 Smith 138148 3,123,862 3/1964 Levey 18163,132,569 5/1964 Shepherd 92-193 3,224,042 10/1965 Meissner 18163,255,490 6/1966 Sturm 18-16 CHARLES W. LANHAM, Primary Examiner.

A. RUDERMAN, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,379,043 April 23, 1968 Francis J. Fuchs, Jr.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 5, line 48, "Pl A2=Pl Al" should read P2 A2=Pl Al line 50,"pressuirzed" should read pressurized Column 9, line 72, after "to"insert the Column 10, line 23, "600)." should read 600), Column 13, line10, "dies" should read die line 38, "pressurzied" should readpressurized Column 14, line 13, comunicating" should read communicatingline 34, "blank 10'' should read blank 100 Column 15, line 20, "means,"should read means line 34, "the" should read and line 46, "an" shouldread a Column 16 lines 4 and 5, "within the innermost cylinders by thepressures within each succeeding outer cylinder, and" should read tocounteract the pressures within the inner cylinders by the pressureswithin each succeeding outer cylinder, and line 23, "pressure" shouldread pressures line 47, "the" should read a Column 19, line 24,"surounding" should read surrounding line 45, "surounding" should readsurrounding Signed and sealed this 9th day of September 19.6

(SEAL) Attest EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. AttestingOfficer Commissioner of Patents

